1. Field of the Invention
The present invention relates to an apparatus and method for ultraviolet fluorescence spectral and color measurements of diamonds, gemstones and the like, and more particularly, to an apparatus and method for measuring the ultraviolet fluorescence spectrum and for calculating the colorimetric data of the ultraviolet fluorescence caused by the ultraviolet radiation of an ultraviolet radiation source in the wavelength range from 200 nm through 400 nm.
2. Description of the Prior Art
Fluorescence is usually measured by fluorescence spectrometers. A fluorescence spectrometer consists of two monochromators. One monochromator provides excitation radiation on a fluorescence sample wavelength by wavelength in the ultraviolet wavelength range, and another monochromator separates the fluorescence emission from the sample into a spectrum in the visible wavelength range for fluorescence spectral measurement (Ohnishi et al, U.S. Pat. No. 3,936,190; White, U.S. Pat. No. 4,022,529; and Linowski et al, U.S. Pat. No. 5,721,613). At each ultraviolet radiation wavelength from the excitation monochromator, the measurement monochromator scans the fluorescence emission in the whole measurement wavelength range. The total emission power of the fluorescence is the sum of the fluorescence emissions measured in the whole measurement wavelength range by the measurement monochromator wavelength by wavelength of the ultraviolet excitation radiation.
Spear et al (U.S. Pat. No. 5,801,819) discloses an apparatus for distinguishing a natural, colorless, or near colorless diamond from a synthetic diamond. The apparatus has a chamber with a flash lamp to provide ultraviolet light below 250 nm. The intensity of ultraviolet fluorescence of a diamond is measured to classify the diamond as probably natural or synthetic.
The intensity and color of fluorescence of diamonds and gemstones are traditionally observed and graded visually by human graders. Under an ultraviolet fluorescent lamp at 365 nm, a human grader observes the color and intensity of the ultraviolet fluorescence of a diamond, and compares the fluorescence intensity of the diamond with the fluorescence intensities of a fluorescence grading master set to assign a fluorescence grade to the diamond graded.
The fluorescence of diamonds and gemstones can also be graded by a diamond fluorescence measuring device (Geurts, U.S. Pat. No. 7,102,742 and U.S. Pat. No. 7,262,835). The device includes a sample chamber with two ultraviolet light emitting diodes (LED) and a light detector. The measured lux reading of the visible fluorescence light is converted into fluorescence grades.
Liu (U.S. Pat. No. 7,652,755) discloses an apparatus and method for color measurement and color grading of diamonds, gemstones and the like. The apparatus comprises a spectrometer, a computer and a dual integrating sphere measurement arrangement. The dual integrating sphere optical arrangement consists of two integrating spheres. One is a measurement integrating sphere and another is a sample integrating sphere. The apparatus can measure the spectral reflectance of a faceted diamond, gemstone or the like in the visible wavelength range, calculate the colorimetric data, and grade the color using the artificial intelligence software with a neural network and a fuzz logic algorithm.
There is no apparatus in the prior art capable for directly measuring ultraviolet fluorescence spectrum and fluorescence color of gemstones, diamonds and the like. There is a need for such an apparatus capable for directly measuring the ultraviolet fluorescence spectrum and fluorescence color diamonds, gemstones, and the like.